This invention pertains to the separation of organic liquids such as alcohols from water solutions containing same, using a multi-stage adsorption process.
Energy-efficient processes for separating alcohols, such as ethanol, from water solutions have been sought in recent years. The objective is to make fermentation ethanol an economic and attractive source of liquid fuels. Conventional distallation separation for ethanol-water solutions requires substantial energy, equivalent to 28-35% of the combustion energy of ethanol (84,800 Btu/gal). This undesirably high energy requirement is due to the multiple liquid-vapor phase changes inherent to fractionating distillation, which are energy intensive operations. Contrarily, adsorption processes for liquid-vapor separation are usually exothermic and require no energy input; only the desorption or releasing the adsorbed material requires some energy or heat input. Based on this concept, a multi-stage adsorption process for ethanol-water separation was conceived and developed which has low energy consumption and low investment costs, and thus is advantageous for the economic production of ethanol and other alcohols.
It is generally known that alcohol vapors can be dried by passing them over adsorbents that selectively adsorb water. Although drying of alcohols and various hydrocarbons by adsorption on molecular sieve is known, such processes are not attractive for removing major portions of water from solutions so as to provide dehydrated products. Thus, an energy-efficient adsorption process for removing major amounts of water from organic liquid solutions has been sought and would be very desirable and economically advantageous.